1. Field of the Invention
The present invention relates to a method and apparatus for forming an image. More particularly, the present invention relates to a method and apparatus for forming an image having a device capable of effectively fixing the image with reduced assembling steps and simple jam clearing operation.
2. Description of the Related Art
Related art image forming apparatuses that use toner to form a visualized image are equipped with a fixing device for fixing a toner image on a recording medium. The fixing device includes a fixing roller or a fixing belt, a pressure roller or a pressure belt, and a nip part, so that the toner held on the recording medium is melt and fixed on the recording medium with pressure. The toner typically includes resin, which melts at the nip part. As a result, the toner tends to adhere to the fixing roller or the fixing belt. Therefore, various countermeasures are taken in order to prevent the toner from adhering to the surface of the fixing roller or the fixing belt.
In addition, related art image forming apparatuses are provided with a sheet separation mechanism having separation pawls that allow the sheet, which tends to wind around the fixing roller or the fixing belt due to molten toner, to forcibly separate from the fixing roller or the fixing belt. However, the separation pawls do not completely prevent the sheet from winding around the fixing roller or the fixing belt. In addition, when a jam caused by a wound sheet occurs, removal of the sheet is difficult. When a user removes the sheet in a condition in which the separation pawls are in contact with the roller, the sheet is torn and the torn sheet remains, which makes removal of the torn sheet difficult.
As one countermeasure for such a disadvantage, a mechanism is known in which the separation pawls are released from the fixing roller or the fixing belt when the user removes a jammed sheet. In order to provide such a mechanism, the separation pawls are formed on a unit capable of being released from the nip part. Each separation pawl includes a pawl part and a rotation shaft, and the pawl part is biased by a spring, so that the pawl part pivoting around the rotation shaft is in contact with a surface of the fixing roller or the fixing belt. As a result, when the unit is released from the nip part while dealing with the jam, this release causes absence of the fixing roller or the fixing belt that normally serves as a counterpart for the separation pawls to be in contact therewith, and the absence of this counterpart further causes the separation pawls to pivot too far inward in a direction of the fixing roller or the fixing belt. When closing and locking the unit after removing the jammed sheet, the separation pawl remains in a condition in which the separation pawl is pivoted too far, and thus the tips of the separation pawls stick into the surface of the fixing roller or the fixing belt and damage the surface thereof.
To prevent the above disadvantage from occurring, upon releasing to open the unit or closing to lock the unit, a mechanism for separating the separation pawls from the fixing roller or the fixing belt is known. A technique associated with a fixing device having such a separation mechanism has a structure as follows. Namely, each of a plurality of separation pawls includes an elastic member so that the separation pawls are forcibly separated from the fixing roller or the fixing belt. When releasing the unit, the elastic member is separated from a regulation member to forcibly separate the separation pawl from the fixing roller or the fixing belt, and when locking the unit after dealing with the jammed sheet the regulation member causes the elastic member to regulate the separation pawl so as not to damage the surface of the fixing roller or the fixing belt
However, a separation pawl mechanism, which brings the separation pawls close to the surface or separating the separation pawls from the surface, regulates each of the plurality of separation pawls, respectively. Accordingly, the number of parts increases which results in an increase in the number of assembly processes when assembling the fixing device. In addition, when doing maintenance, there is a disadvantage that a lot of time is required to replace the separation pawls.